S5 6-port block
S5 turbo
FMIC
2.5-3" exhaust

My issue is this time around with this setup I've had some boost control issues. My old HKS EVC was having trouble keeping the boost steady at 10psi. Took it off and just ran the wastegate.
The boost controller was working fine, holding boost with the same exhaust/intake, when the last motor blew. So, I've been doing some troubleshooting to see if it really was the problem. Today I unhooked to wastgate actuator from the wastegate just to see what the wastegate port was actually doing. Did a full pull in 3rd. Boosted (slowly) to 10psi then creeped DOWN to 5-6. Is this right?

I'm just trying to eliminate possible factors to my boost controller issues.

So you disconnected the wastegate actuator and left the door to move freely? If so, the expectation would be little to no boost if the wastegate port size is large enough to bypass enough exhaust. But with the door able to move on its own, I'd wonder if the main exhaust flow could be forcing the door closed. It'd have to be wired open to be sure that doesn't happen.

What was the result when you ran off the wastegate spring alone?

port the wastegate as best you can, you won't be able to much with the series 5 but it should give some improvement. problem is the 9.7:1 rotors and that tiny turbo are going to creep with the stock wastegate.

Here's a good "How to" -> FC3S Pro: S5 Wastegate Porting

With everything hooked up with just the wastegate it's a pretty solid 10psi.

One of the things on my winter list is to port the wastegate. Planning on doing a boost leak test soon too.